Lambda bun runtime

This repository contains custom built bun runtime for AWS Lambda. It also contains CDK constructs for BunFunction which uses BunLambdaLayer.

Bun is a fast JavaScript runtime.

Current bun version: 1.3.6

Installation

You can install current version of our Lambda bun runtime from npm like this:

npm i @beesolve/lambda-bun-runtime

Usage

There are two constructs which you can use right ahead - BunFunction which depends on BunLambdaLayer:

import { BunLambdaLayer, BunFunction } from '@beesolve/lambda-bun-runtime';
import { Duration } from "aws-cdk-lib";

const bunLayer = new BunLambdaLayer(this, "BunLayer");

const apiHandler = new BunFunction(this, "ApiHandler", {
  entrypoint: `${__dirname}/dist/api.js`,
  memorySize: 1024,
  timeout: Duration.seconds(10),
  environment: {
    STAGE: 'prod',
  },
  bunLayer,
});

You can pass additional properties to both BunLambdaLayer and BunFunction.

The code for BunFunction needs to be built beforehand.

We recommend to use following build script as quick start:

// build.ts
import * as Bun from "bun";
import { rmSync } from "node:fs";

console.time("Built.");

rmSync("dist", { force: true, recursive: true });

await Bun.build({
  entrypoints: ["api.ts"],
  outdir: "dist",
  target: "bun", // this is important as the built code runs in Bun environment
  minify: true,
  splitting: true,
  sourcemap: "inline",
});

console.timeEnd("Built.");

When you persist above build script in build.ts you can then run it with bun run build.ts.

Why the fork?

This runtime is fork of official bun-lambda. It was created because it seems that Lambda is not very high on Bun's roadmap and there are multiple pull requests which haven't been merged.

The usage is the same as in official runtime.

Here are changes which were added on top of the original runtime:

• https://github.com/oven-sh/bun/pull/17449 - traceId is not guaranteed in all Lambda environments so exitting when traceId is not present has been removed
• https://github.com/oven-sh/bun/pull/21018 - setting cookies now works with both HTTP Event v1 and HTTP Event v2
• https://github.com/oven-sh/bun/pull/20640 - when using API Gateway Authorizer the authorization context is present in Request header called x-amzn-authorizer

Roadmap

• [x] keep in sync with latest versions of Bun
• [ ] investigate https://github.com/oven-sh/bun/pull/20825
• [ ] investigate https://github.com/oven-sh/bun/issues/14139
• [ ] investigate https://github.com/oven-sh/bun/issues/6003
• [ ] investigate https://github.com/oven-sh/bun/issues?q=is%3Aissue%20state%3Aopen%20label%3Alambda
• [ ] implement automatic code bundling with BunFunction